tmux on startup and ssh-agent forwarding issue

Question

I've added the following lines (taken from here) to my .bashrc to automatically start a tmux session on login:

if [ "$PS1" != "" -a "${STARTED_TMUX:-x}" = x -a "${SSH_TTY:-x}" != x ]
then
        STARTED_TMUX=1; export STARTED_TMUX
        sleep 1
        ( (tmux has-session -t remote && tmux attach-session -t remote) || (tmux new-session -s remote) ) && exit 0
        echo "tmux failed to start"
fi

However, this seems to breaks ssh agent forwarding on subsequent logins. Is there a way around this?

Answer 1

You can use this pattern to solve your problem: http://superuser.com/questions/180148/how-do-you-get-screen-to-automatically-connect-to-the-current-ssh-agent-when-re

That allows you to have the SSH agent connection dynamically updated to reflect each connection; I think it uses screen, but tmux should be very much the same pattern.

The principal is to use a symlink to the SSH agent socket, which can change, inside tmux - and then update that symlink when you connect in a new SSH session.